Discrete R symmetries always play an important role in low energy SUSY. The
spontaneously broken of such discrete R symmetries, for example, by gaugino
condensation, can lead to domain walls, which need to be either inflated away
or collapse to avoid cosmic difficulties. We propose that explicitly R symmetry
violation needed for collapse of domain walls can be the consequence of
multiple sector SUSY breaking. The consistency constraints for the generation
of non-problematic domain walls from gaugino condensation are discussed. We
also study the emitted gravitational waves related to the collapse of domain
walls. We find that, for SUSY breaking scale of order O(1)GeV
in one of the sequestered sector (and also a low reheating temperature of order
MeV if the reheating is not completed when the domain walls collapse),
the peak frequency of gravitational waves emitted can lie at nHz. Such a low
SUSY breaking scale can be consistency and natural in multiple sector SUSY
breaking scenario. The GWs signal by NANOGrav could be a signal of such
multiple sector SUSY breaking scenario and it may also indicate the existences
of light goldstini at eV mass scale.Comment: 13 page